The :first-child pseudo-class matches an element that is the first child element of some other element.
:link , :visited , :hover , :active , :focus
The :link pseudo-class applies for links that have not yet been visited.
The :visited pseudo-class applies once the link has been visited by the user.
The :hover pseudo-class applies while the user designates an element (with some pointing device), but does not activate it.
The :active pseudo-class applies while an element is being activated by the user. For example, between the times the user presses the mouse button and releases it.
The :focus pseudo-class applies while an element has the focus (accepts keyboard events or other forms of text input).
The :first-line pseudo-element applies special styles to the contents of the first formatted line of a paragraph.
The :first-letter pseudo-element may be used for "initial caps" and "drop caps", which are common typographical effects. This type of initial letter is similar to an inline-level element if its 'float' property is 'none', otherwise it is similar to a floated element.